Electric power tools such as portable electric drills, circular saws, jigsaws, sanders, and the like are widely known in the art. Generally, they include an electric motor for rotatably driving a shaft, with a tool such as a drill bit, a saw blade, or the like attached to the shaft. The electric motor is often an AC or DC motor that includes a rotating armature with a commutator. Two non-rotating conducting brushes electrically contact the commutator. The motor assembly, including the armature, the commutator and the brushes, is enclosed in a housing. The brushes must be urged into engagement with the commutator with a spring to ensure good contact with the, provide some degree of tolerance, and also compensate for wear of the brush.
Because electrical current flows through each of the brushes, they are often movably held in an insulating brush box or holder. The brush holder insulates the brush from the housing. The spring which biases the brush into engagement with the commutator is typically contained in the brush holder, and the brush (or the spring) is electronically connected to have a power source such as an AC supply or a DC battery.
During manufacture of such tools in the prior art, the motor armature and commutator were provided pre-assembled, and installed in the housing at the time of final tool assembly. Each brush and brush holder were likewise provided as a pre-assembled unit and installed in the housing at the time of final tool assembly. To speed and simplify tool assembly, the brush holder may have been installed through an open end of the housing by placing it in a bracket that has been pre-formed in the housing. To retain the brush holder in place in the bracket, a housing end cap had either a brush holder locking assembly extending therefrom, so that when the end cap was attached to the housing, the holder locking assembly locked the brush holder in place, or a screw or screws that secure the brush holder to the housing.
To allow for some tolerance in housings and brush holders, and to provide for long service life of the tool, the brush holder locking assembly included a spring member such as a rubber-like polymer layer or pad for engaging the brush holder. By way of particular example, one known tool assembly included a housing end cap having a hollow brush assembly support tube connected thereto. A resilient polymer bumper pad with a barrel portion was inserted into the hollow tube, and had a brush holder-engaging portion that engaged the brush holder. The bumper pad held the brush holder in place, and also provided a degree of protective cushion to the holder to prevent holder breakage if the tool was dropped on its end cap. This known configuration, however, was time consuming to install in the housing.
The commercial market for such tools is competitive, with a large number of competitors vying for market share. In this competitive environment, there are strong business incentives to keep manufacturing costs low. Accordingly, it is desirable to reduce the number of parts and the number of steps required to manufacture the tools.
These and other needs remain unresolved in the art.